Hardware - Homepage | Wiley · Computer hardware is composed of the ... is 00101011 in ASCII. The 256 characters and symbols that ... Cycle times 100 millisecs 10 microsecs 500 nanosecs

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TG1-1

T E C H N O L O G Y G U I D E

1Hardware

T1.1What Is a Computer System?

T1.2The Evolution of Computer

Hardware

T1.3Types of Computers

T1.4The Microprocessor and

Primary Storage

T1.5Input/Output Devices

This guide was updated by Linda Lai, at City Univer-sity of Hong Kong.

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TG1-2 TECHNOLOGY GUIDE 1 HARDWARE

T1.1 WHAT IS A COMPUTER SYSTEM?Computer hardware is composed of the following components: central process-ing unit (CPU), input devices, output devices, primary storage, secondary stor-age, and communication devices. (These devices are described in TechnologyGuide 4.) Each of the hardware components plays an important role in com-puting. The input devices accept data and instructions and convert them to aform that the computer can understand. The output devices present data in aform people can understand. The CPU manipulates the data and controls thetasks done by the other components. The primary storage (internal storage)temporarily stores data and program instructions during processing. It also storesintermediate results of the processing. The secondary storage (external) storesdata and programs for future use. Finally, the communication devices providefor the flow of data from external computer networks (e.g., Internet, intranets)to the CPU, and from the CPU to computer networks. A schematic view of acomputer system is shown in Figure T-1.1.

Representing Data,Pictures, Time, andSize in a Computer

ASCII. Today’s computers are based on integrated circuits (chips), each of whichincludes millions of subminiature transistors that are interconnected on a small(less than 1-inch-square) chip area. Each transistor can be in either an “on” or“off” position.

The “on-off” states of the transistors are used to establish a binary 1 or 0 forstoring one binary digit, or bit. A sufficient number of bits to represent specificcharacters—letters, numbers, and special symbols—is known as a byte, usually8 bits. Because a bit has only two states, 0 or 1, the bits comprising a byte canrepresent any of 28, or 256, unique characters. Which character is representeddepends upon the bit combination or coding scheme used. The two most com-monly used coding schemes are ASCII (American National Standard Codefor Information Interchange), pronounced “ask-ee,” and EBCDIC (ExtendedBinary Coded Decimal Interchange Code), pronounced “ebsa-dick.” EBCDICwas developed by IBM and is used primarily on large, mainframe computers.ASCII has emerged as the standard coding scheme for microcomputers. Thesecoding schemes, and the characters they present, are shown in Figure T-1.2. In

InputDevices

CommunicationDevices

OutputDevices

SecondaryStorage

ControlUnitBus

Bus

ExternalNetwork

Bus Bus

Arithmetic-LogicUnit

Primary Storage

Central Processing Unit

FIGURE T-1.1 Thecomponents of computerhardware. A “bus” is aconnecting channel.

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T1.1 WHAT IS A COMPUTER SYSTEM? TG1-3

addition to characters, it is possible to represent commonly agreed-upon symbolsin a binary code. For example, the plus sign (�) is 00101011 in ASCII.

The 256 characters and symbols that are represented by ASCII and EBCDICcodes are sufficient for English and Western European languages but are not largeenough for Asian and other languages that use different alphabets. Unicode isa 16-bit code that has the capacity of representing more than 65,000 charactersand symbols. The system employs the codes used by ASCII and also includesother alphabets (such as Cyrillic and Hebrew), special characters (including reli-gious symbols), and some of the “word writing” symbols used in various Asiancountries.

REPRESENTING PICTURES. Pictures are represented by a grid overlay of the pic-ture. The computer measures the color (or light level) of each cell of the grid.The unit measurement of this is called a pixel. Figure T-1.3 shows a pixel rep-resentation of the letter A and its conversion to an input code.

Character

ABCDEFGHIJKLMNOPQR

EBCDIC Code

110000011100001011000011110001001100010111000110110001111100100011001001110100011101001011010011110101001101010111010110110101111101100011011001

ASCII Code

101000011010001010100011101001001010010110100110101001111010100010101001101010101010101110101100101011011010111010101111101100001011000110110010

Character

STUVWXYZ0123456789

EBCDIC Code

111000101110001111100100111001011110011011100111111010001110100111110000111100011111001011110011111101001111010111110110111101111111100011111001

ASCII Code

101100111011010010110101101101101011011110111000101110011011101001010000010100010101001001010011010101000101010101010110010101110101100001011001

FIGURE T-1.2 Internalcomputing codingschemes.

FIGURE T-1.3 Pixelrepresentation of the letter A. Pixel diagram Input code

REPRESENTING TIME AND SIZE OF BYTES. Time is represented in fractions ofa second. The following are common measures of time:

� Millisecond � 1�1000 second� Microsecond � 1�1,000,000 second� Nanosecond � 1�1,000,000,000 second� Picosecond � 1�1,000,000,000,000 second



T1.2 THE EVOLUTION OF COMPUTER HARDWARE

Size is measured by the number of bytes. Common measures of size are:

� Kilobyte � 1,000 bytes (actually 1,024)� Megabyte � 1,000 kilobytes � 106 bytes� Gigabyte � 109 bytes� Terabyte � 1012 bytes� Petabyte � 1015 bytes� Exabyte � 1018 bytes

TABLE T-1.1 Hardware Generations

Generations

Feature 1st 2nd 3rd 4th (early) 4th (1988) 4th (2001)

Circuitry Vacuum tubes Transistors Integrated LSI and VLSI ULSI GSIcircuits

Primary 2 KB 64 KB 4 MB 16 MB 64 MB 128 MBstorage

Cycle times 100 millisecs 10 microsecs 500 nanosecs 800 picosecs 2,000 picosecs 333 MHzAverage cost $2.5 million $250 thousand $25 thousand $2.5 thousand $2.0 thousand $1.5 thousand

Computer hardware has evolved through four stages, or generations, of tech-nology. Each generation has provided increased processing power and storage ca-pacity, while simultaneously exhibiting decreases in costs (see Table T-1.1). Thegenerations are distinguished by different technologies that perform the pro-cessing functions.

The first generation of computers, 1946–1956, used vacuum tubes to store andprocess information. Vacuum tubes consumed large amounts of power, gener-ated much heat, and were short-lived. Therefore, first-generation computers hadlimited memory and processing capability.

The second generation of computers, 1957–1963, used transistors for storingand processing information. Transistors consumed less power than vacuum tubes,produced less heat, and were cheaper, more stable, and more reliable. Second-generation computers, with increased processing and storage capabilities, beganto be more widely used for scientific and business purposes.

Third-generation computers, 1964–1979, used integrated circuits for stor-ing and processing information. Integrated circuits are made by printing numer-ous small transistors on silicon chips. These devices are called semiconductors. Third-generation computers employed software that could be used by nontechnicalpeople, thus enlarging the computer’s role in business.

Early to middle fourth-generation computers, 1980–1995, used very large-scale integrated (VLSI) circuits to store and process information. The VLSItechnique allows the installation of hundreds of thousands of circuits (transistorsand other components) on a small chip. With ultra-large-scale integration(ULSI), 10 million transistors could be placed on a chip. These computers areinexpensive and widely used in business and everyday life.

A chip showing circuitlines.


T1.3 TYPES OF COMPUTERS TG1-5

Fifth-GenerationComputers

Future Generationsof Computers

Late fourth-generation computers, 1996–present, use grand-scale integrated(GSI) circuits to store and process information. With GSI, 1,000 million tran-sistors can be placed on a chip.

The first four generations of computer hardware are based on the Von Neumannarchitecture, which processed information sequentially, one instruction at a time.The fifth generation of computers uses massively parallel processing to processmultiple instructions simultaneously. Massively parallel computers use flexiblyconnected networks linking thousands of inexpensive, commonly used chips toaddress large computing problems, attaining supercomputer speeds. With enoughchips networked together, massively parallel machines can perform more than atrillion floating point operations per second—a teraflop. A floating point operation(flop) is a basic computer arithmetic operation, such as addition or subtraction,on numbers that include a decimal point.

Two major innovations are in experimental stages: DNA computers and opticalcomputers.

DNA COMPUTERS. DNA is an acronym for deoxyribonucleic acid, the compo-nent of living matter that contains the genetic code. Scientists are now experi-menting with DNA computing, which takes advantage of the fact that informationcan be written onto individual DNA molecules. The information uses the alpha-bet of four bases that all living organisms use to record genetic information. ADNA computation is done by coding a problem into the alphabet and then cre-ating conditions under which DNA molecules are formed that encode all possi-ble solutions of a problem. The process produces billions of molecules encodingwrong answers, and a few encoding the right one. Modern molecular geneticshas chemical procedures that can reliably isolate the few DNA molecules encod-ing the correct answer from all the others.

DNA computers process in parallel and are potentially twice as fast as today’sfastest supercomputers. In addition, storage on DNA computers is vastly im-proved. Modern storage media store information at a density of one bit per 1,012nanometers (one billionth of a meter), while DNA computers have storage den-sities of one bit per cubic nanometer, a trillion times less space.

OPTICAL COMPUTERS. Scientists are working on a machine that uses beams oflight instead of electrons. Called optoelectronic, these computers are expected toprocess information several hundred times faster than current computers.

Supercomputers

T1.3 TYPES OF COMPUTERS

Computers are distinguished on the basis of their processing capabilities. Com-puters with the most processing power are also the largest and most expensive.

Supercomputers are the computers with the most processing power. The pri-mary application of supercomputers has been in scientific and military work, buttheir use is growing rapidly in business as their prices decrease. Supercomputersare especially valuable for large simulation models of real-world phenomena,where complex mathematical representations and calculations are required, or


FIGURE T-1.4Supercomputers vs.neural computing ( Xis a CPU).


for image creation and processing. Supercomputers are used to model the weatherfor better weather prediction, to test weapons nondestructively, to design aircraft(e.g., the Boeing 777) for more efficient and less costly production, and to makesequences in motion pictures (e.g., Jurassic Park). Supercomputers generally op-erate 4 to 10 times faster than the next-most-powerful computer class, the main-frame. By 2001, supercomputers were able to compute one trillion operationsper second. This represented a 1,000-fold speed increase over 1990’s most pow-erful computers. In 2001, the prices of supercomputers range from $100,000 to$15 million or more.

Supercomputers use the technology of parallel processing. However, incontrast to neural computing, which uses massively parallel processing, super-computers use noninterconnected CPUs. The difference is shown in Figure T-1.4.Parallel processing is also used today in smaller computers where 2 to 64 proces-sors are common.

Massively ParallelComputers

Mainframes

InputOutput

Input(s)

Output(s)

Supercomputers Massively Parallel(neural computing)

xxxx

xxxx

xxx

xx

A supercomputer.

The development of massively parallel computers has led some people to confusethese computers with supercomputers. The massively parallel computers area relatively new type of computer that uses a large number of processors. Theprocessors divide up and independently work on small chunks of a large prob-lem. Modern problems in science and engineering, such as structural engineer-ing, fluid mechanics, and other large-scale physical simulations, rely on high-performance computing to make progress. These problems are so enormous asto swamp the computational power of conventional computers, so massively par-allel computers must be used. In 2001, the prices of massively parallel comput-ers range from $100,000 to $4 million or more.

Mainframes are not as powerful and generally not as expensive as supercom-puters. Large corporations, where data processing is centralized and large data-bases are maintained, most often use mainframe computers. Applications thatrun on a mainframe can be large and complex, allowing for data and informa-tion to be shared throughout the organization. In 2001, a mainframe system hadanywhere from 50 megabytes to several gigabytes of primary storage. Online sec-ondary storage may use high-capacity magnetic and optical storage media with ca-pacities in the gigabyte to terabyte range. Additionally, offline storage often useshigh-capacity magnetic tape systems. Several hundreds or even thousands of on-line computers can be linked to a mainframe. In 2001, mainframes were pricedas high as $5 million.


T1.3 TYPES OF COMPUTERS TG1-7

Minicomputers, also called midrange computers, are smaller and less expensivethan mainframe computers. Minicomputers are usually designed to accomplishspecific tasks such as process control, scientific research, and engineering appli-cations. In 2001, a minicomputer system had anywhere from 10 megabytes toover 1 gigabyte of primary storage, and their prices ranged from $10,000 to$250,000.

Larger companies gain greater corporate flexibility by distributing data pro-cessing with minicomputers in organizational units instead of centralizing com-puting at one location. These minicomputers are connected to each other andoften to a mainframe through telecommunication links. The minicomputer is alsoable to meet the needs of smaller organizations that would rather not utilizescarce corporate resources by purchasing larger computer systems.

Vendors originally developed workstations to provide the high levels of perfor-mance demanded by these users. Workstations are often based on RISC (re-duced instruction set computing) architecture and provide both very-high-speedcalculations and high-resolution graphic displays. These computers have foundwidespread acceptance within the scientific community and, more recently,within the business community.

A workstation has more powerful mathematical and graphical processing ca-pability. In 2001, a workstation system had anywhere from 64 megabytes to 512megabytes of primary storage and ranged in price from $2,000 to $10,000. How-ever, the distinction between workstations and personal computers is rapidly blur-ring. The latest PCs have the computing power of recent workstations. Low-endworkstations are now indistinguishable from high-end PCs.

Microcomputers, also called micros or personal computers (PCs), are the smallestand least expensive category of general-purpose computers. In general, modernmicrocomputers have between 8 and 128 megabytes of primary storage, one 3.5-inch floppy drive, a CD-ROM drive, and one gigabyte or more of secondary stor-age. They may be subdivided into four classifications based on their size: desk-tops, laptops, notebooks, and palmtops.

The desktop personal computer is the typical, familiar microcomputer sys-tem. It is usually modular in design, with separate but connected monitor, key-board, and CPU. Laptop computers are small, easily transportable, lightweightmicrocomputers that fit easily into a briefcase. Notebooks are smaller laptops

Minicomputers

Workstations

Microcomputers(PCs)

A mainframe computer.



(also called mini-laptops), but sometimes are used interchangeably with laptops.Laptops and notebooks are designed for maximum convenience and transpor-tability, allowing users to have access to processing power and data without be-ing bound to an office environment.

Palmtop computers are handheld microcomputers small enough to carryin one hand. Although still capable of general-purpose computing, palmtops areusually configured for specific applications and limited in the number of waysthey can accept user input and provide output.

PERSONAL DIGITAL ASSISTANT. A personal digital assistant (PDA) is a palm-top computer that combines a fast processor with a multitasking operating sys-tem using a pen for handwriting recognition rather than keyboard input. PDAsdiffer from other personal computers in that they are usually specialized for in-dividual users. The PDA may be thought of as a computing appliance, rather thana general-purpose computing device. In 2001, PDAs often weigh under a poundand are priced from $150 to $500. Some PDAs enable users to communicate viafax, electronic mail, and paging, or to access online services. PDAs are very pop-ular for special applications, such as the New York Stock Exchange.

PDAs from Palm, Inc. have emerged as a solid wireless communications tool.The Palm™ VIIx handheld features a built-in modem that allows users to wire-lessly connect to the Internet, plus send and receive e-mail. To view Web con-tent, the Palm VIIx handheld uses technology the company calls “Web clipping.”Web clipping is an efficient way for people on the move to access Web informa-tion without a PC. Users can download Web-clipping applications to get stockquotes, sports scores, today’s headlines, and tomorrow’s weather.

SMART CARDS. An even smaller form of computer is the smart card, whichhas resulted from the continuing shrinkage of integrated circuits. Similar in sizeand thickness to ordinary plastic credit cards, smart cards contain a small CPU,memory, and an input/output device that allow these “computers” to be used ineveryday activities such as person identification and banking.

Uses for smart cards are appearing rapidly. People are using them as check-books; a bank ATM (automatic teller machine) can “deposit money” into thecard’s memory for “withdrawal” at retail stores (see Chapter 5). Smart cards arebeing used to transport data between computers, replacing floppy disks. Adding

A desktop computer (a), an IBM Thinkpad® laptop (b), and a SONY laptop notebook computer (c).

(a) (b) (c)

A Palm PDA. (Palm is atrademark of Palm, Inc.)


T1.4 THE MICROPROCESSOR AND PRIMARY STORAGE TG1-9

Network Computersand Terminals

a small transmitter to a smart card can allow businesses to locate any employeeand automatically route phone calls to the nearest telephone.

The computers described so far are considered “smart” computers. However,mainframe and midrange computers also can use dumb terminals, which are ba-sically input/output devices. However, as time passed, these terminals, which arecalled X terminals, have also come to be used for limited processing. Two exten-sions of these terminals are discussed here.

NETWORK COMPUTERS. A network computer (NC), also called a thin com-puter, is a desktop terminal that does not store software programs or data per-manently. Similar to a dumb terminal, the NC is simpler and cheaper than a PCand easy to maintain. Users can download software or data they need from aserver on a mainframe over an intranet or the Internet. There is no need for harddisks, floppy disks, CD-ROMs and their drives. The central computer can saveany material for the user.

The NC’s cost in 2001 is $300 to $600. At the same time, simple PCs are sell-ing for $600 to $800. Since the price advantage is not so large, the future of NCsis not clear. However, there is a potentially substantial saving in the maintenancecost. The NCs provide security as well. However, users are limited in what theycan do with the terminals.

WINDOWS-BASED TERMINALS (WBTs). Windows-based terminals (WBTs)are a subset of the NC. Although they offer less functionality than PCs, WBTs re-duce maintenance and support costs and maintain compatibility with Windowsoperating systems. WBT users access Windows applications on central servers asif those applications were running locally. As with the NC, the savings are notonly in the cost of the terminals, but mainly from the reduced support and main-tenance cost.

The WBT is used by some organizations as an alternative to NCs. However,because the NCs use Java and HTML languages, they are more flexible and effi-cient and less expensive to operate than a WBT.

Smart cards.

T1.4 THE MICROPROCESSOR AND PRIMARY STORAGE

The central processing unit (CPU) is also referred to as a microprocessor becauseof its small size. The CPU is the center of all computer-processing activities, whereall processing is controlled, data are manipulated, arithmetic computations are

The CentralProcessing Unit

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Primary Storage

Buses

performed, and logical comparisons are made. The CPU consists of the controlunit, the arithmetic-logic unit (ALU), and the primary storage (or main memory).

The arithmetic-logic unit performs required arithmetic and comparisons,or logic, operations. The ALU adds, subtracts, multiplies, divides, compares, anddetermines whether a number is positive, negative, or zero. All computer appli-cations are achieved through these six operations. The ALU operations are per-formed sequentially, based on instructions from the control unit. For these op-erations to be performed, the data must first be moved from the storage to thearithmetic registers in the ALU. Registers are specialized, high-speed memoryareas for storing temporary results of ALU operations as well as for storing cer-tain control information.

Primary storage, or main memory, stores data and program statements forthe CPU. It has four basic purposes:

1. To store data that have been input until they are transferred to the ALU forprocessing

2. To store data and results during intermediate stages of processing

3. To hold data after processing until they are transferred to an output device

4. To hold program statements or instructions received from input devices andfrom secondary storage

Primary storage in today’s microcomputers utilizes integrated circuits.These circuits are interconnected layers of etched semiconductor materials form-ing electrical transistor memory units with “on-off” positions that direct the elec-trical current passing through them. The on-off states of the transistors are usedto establish a binary 1 or 0 for storing one binary digit, or bit.

Instructions and data move between computer subsystems and the processor viacommunications channels called buses. A bus is a channel (or shared data path)through which data are passed in electronic form. Three types of buses link theCPU, primary storage, and the other devices in the computer system. The databus moves data to and from primary storage. The address bus transmits signalsfor locating a given address in primary storage. The control bus transmits sig-nals specifying whether to “read” or “write” data to or from a given primary stor-age address, input device, or output device.

The capacity of a bus, called bus width, is defined by the number of bitsthey carry at one time. (The most common PC in 2001 was 64 bits.) Bus speedsare also important, currently averaging about 133 megahertz (MHz).

Controlunit

Arithmetic/logic unit

Random-access memory

Processor

Primary Storage

A CPU.

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Control Unit

Arithmetic-LogicUnit

The control unit reads instructions and directs the other components of thecomputer system to perform the functions required by the program. It interpretsand carries out instructions contained in computer programs, selecting programstatements from the primary storage, moving them to the instruction registers inthe control unit, and then carrying them out. It controls input and output de-vices and data-transfer processes from and to memory. The control unit does notactually change or create data; it merely directs the data flow within the CPU.The control unit can process only one instruction at a time, but it can executeinstructions so quickly (millions per second) that it can appear to do many dif-ferent things simultaneously.

The series of operations required to process a single machine instruction iscalled a machine cycle. Each machine cycle consists of the instruction cycle, whichsets up circuitry to perform a required operation, and the execution cycle, duringwhich the operation is actually carried out.

There are two categories of memory: the register, which is part of the CPU and isvery fast, and the internal memory chips, which reside outside the CPU andare slower. A register is circuitry in the CPU that allows for the fast storage andretrieval of data and instructions during the processing. The control unit, theCPU, and the primary storage all have registers. Small amounts of data reside inthe register for very short periods, prior to their use.

The internal memory is used to store data just before they are processedby the CPU. Immediately after the processing it comprises two types of storagespace: RAM and ROM.

RANDOM-ACCESS MEMORY. Random-access memory (RAM) is the place inwhich the CPU stores the instructions and data it is processing. The larger thememory area, the larger the programs that can be stored and executed.

With the newer computer operating system software, more than one pro-gram may be operating at a time, each occupying a portion of RAM. Most per-sonal computers as of 2001 needed 64 to 128 megabytes of RAM to process “multimedia” applications, which combine sound, graphics, animation, and video,thus requiring more memory.

The advantage of RAM is that it is very fast in storing and retrieving any typeof data, whether textual, graphical, sound, or animation-based. Its disadvantagesare that it is relatively expensive and volatile. This volatility means that all dataand programs stored in RAM are lost when the power is turned off. To lessenthis potential loss of data, many of the newer application programs perform pe-riodic automatic “saves” of the data.

Many software programs are larger than the internal, primary storage (RAM)available to store them. To get around this limitation, some programs are dividedinto smaller blocks, with each block loaded into RAM only when necessary. How-ever, depending on the program, continuously loading and unloading blocks canslow down performance considerably, especially since secondary storage is somuch slower than RAM. As a compromise, some architectures use high-speedcache memory as a temporary storage for the most frequently used blocks. Thenthe RAM is used to store the next most frequently used blocks, and secondarystorage (described later) for the least used blocks.

Since cache memory operates at a much higher speed than conventional mem-ory (i.e., RAM), this technique greatly increases the speed of processing because



MicroprocessorSpeed

it reduces the number of times the program has to fetch instructions and datafrom RAM and secondary storage.

Dynamic random access memories (DRAMs) are the most widely usedRAM chips. These are known to be volatile since they need to be recharged andrefreshed hundreds of times per second in order to retain the information storedin them.

Synchronous DRAM (SDRAM) is a relatively new and different kind ofRAM. SDRAM is rapidly becoming the new memory standard for modern PCs.The reason is that its synchronized design permits support for the much higherbus speeds that have started to enter the market.

READ-ONLY MEMORY. Read-only memory (ROM) is that portion of primarystorage that cannot be changed or erased. ROM is nonvolatile; that is, the programinstructions are continually retained within the ROM, whether power is suppliedto the computer or not. ROM is necessary to users who need to be able to restorea program or data after the computer has been turned off or, as a safeguard, toprevent a program or data from being changed. For example, the instructionsneeded to start, or “boot,” a computer must not be lost when it is turned off.

Programmable read-only memory (PROM) is a memory chip on whicha program can be stored. But once the PROM has been used, you cannot wipeit clean and use it to store something else. Like ROMs, PROMs are nonvolatile.

Erasable programmable read-only memory (EPROM) is a special typeof PROM that can be erased by exposing it to ultraviolet light.

OTHER MEMORY MEASURES. Several other types of memories are on the mar-ket. Notable are the fast static RAM (SRAM) chips and the Flash Memory.

The speed of a chip depends on four things: the clock speed, the word length,the data bus width, and the design of the chip. The clock, located within the con-trol unit, is the component that provides the timing for all processor operations.The beat frequency of the clock (measured in megahertz [MHz] or millions ofcycles per second) determines how many times per second the processor per-forms operations. In 2001, PCs with Pentium 4, Pentium III, P6, PowerPC, or Al-pha chips are running at 700 MHz–1.5 GHz. All things being equal, a processorthat uses a 800 MHz clock operates at twice the speed of one that uses a 400MHz clock. A more accurate processor speed within a computer is millions of in-structions per second (MIPS).

Word length is the number of bits that can be processed at one time by a chip.Chips are commonly labeled as 8-bit, 16-bit, 32-bit, 64-bit, and 128-bit devices.A 64-bit chip, for example, can process 64 bits of data in a single cycle. The largerthe word length, the faster the chip speed.

The width of the buses determines how much data can be moved at one time.The wider the data bus (e.g., 64 bits), the faster the chip. Matching the CPU toits buses can affect performance significantly. In some personal computers, theCPU is capable of handling 64 bits at a time, but the buses are only 32 bits wide.In this case, the CPU must send and receive each 64-bit word in two 32-bitchunks, one at a time. This process makes data transmission times twice as long.

A computer system with two or more processors is referred to as a parallel pro-cessing system. Today, some PCs have 2 to 4 processors while workstations have20 or more. Processing data in parallel speeds up processing. Larger computers

Parallel Processing



MicroprocessorEvolution

may have a hundred processors. For example, IBM is building a supercomputerfor the U.S. Energy Department with 8,192 processors working in tandem andable to execute 10 trillion calculations per second (about 150,000 times fasterthan the 1999 PC).

As described earlier, systems with large numbers of processors are called mas-sively parallel processor (MPP) systems. They are related to neural computing andcomplex scientific applications.

Table T-1.2 shows the evolution of the microprocessor from the introduction of the4004 in 1971 to 2001’s Pentium 4 microprocessors. Over the thirty years, micro-processors have become dramatically faster, more complex, and denser, with in-creasing numbers of transistors embedded in the silicon wafer. As the transistorsare packed closer together and the physical limits of silicon are approached, sci-entists are developing new technologies that increase the processing power of chips.

Chips are now being manufactured from gallium arsenide (GaAs), a semi-conductor material inherently much faster than silicon because electrons canmove through GaAs five times faster than they can move through silicon. GaAschips are more difficult to produce than silicon chips, resulting in higher prices.However, chip producers are perfecting manufacturing techniques that will re-sult in a decrease in the cost of GaAs chips.

Intel has incorporated MMX (multimedia extension) technology in its Pen-tium microprocessors. MMX technology improves video compression/decom-pression, image manipulation, encryption, and input/output processing, all ofwhich are used in modern office software suites and advanced business media,communications, and Internet capabilities.

The Intel Pentium 4 processor introduces a new generation of processingpower with Intel NetBurst microarchitecture. It maximizes the performance of

TABLE T-1.2 Evolution of Microprocessors

Introduction Number of AddressableChip Date Clock Speed Bus Width Transistors Memory

4004 11/71 108 KHz 4 bits 2,300 640 bytes8008 4/72 108 KHz 8 bits 3,500 16 Kbytes8080 4/74 2 MHz 8 bits 6,000 64 Kbytes8086 6/78 5–10 MHz 16 bits 29,000 1 Mbyte80286 2/82 8–12 MHz 16 bits 134,000 16 Mbytes80386 DX 10/85 16–33 MHz 16 bits 275,000 1 Gbyte80386 SX 6/88 16–20 MHz 16 bits 275,000 1 Gbyte80486 DX 4/89 25–50 MHz 32 bits 1.2 M 4 Gbytes80486 SX 4/91 16–33 MHz 32 bits 1.185 M 4 GbytesPentium 3/93 60–166 MHz 32 bits 3.1 M 4 GbytesPentium Pro 3/95 150–200 MHz 32 bits 5.5 M 4 GbytesPentium II 1996 233–300 MHz 32 bits 5.5 M 4 GbytesP6 1997 up to 400 MHz 32 bits 7.5 M 4 GbytesMerced (IA64) 1998/99 500–600 MHz 64 bits 9 M 4–8 GbytesPentium III 1999 450–600 MHz 64 bits 9.5 M 10–12 GbytesItanium (Merced) 2000 800–1,000 MHz 64 bits 25 M 16 GbytesPentium 4 2001 1.3–1.5 GHz 64 bits 42 M 4–64 Gbytes



T1.5 INPUT/OUTPUT DEVICES

cutting-edge technologies such as digital video and online 3-D gaming, and hasan innovative design capable of taking full advantage of emerging Web tech-nologies. The chip’s all-new internal design includes a rapid execution engineand a 400 MHz system bus in order to deliver a higher level of performance.

A prototype plasma-wave chip has been developed that transmits signals as waves,not as packets of electrons as current chips do. Developers use an analogy withsound. Sound travels through the air as waves, not as batches of air molecules thatleave one person’s mouth and enter another’s ear. If sound worked in that fashion,there would be a long delay while the sound-carrying molecules negotiated theirway through the other air molecules. The new chips have the potential of operat-ing speeds in the gigahertz range, or billions of cycles per second.

The arrangement of the components and their interactions is called computer ar-chitecture. Computer architecture includes the instruction set and the number ofthe processors, the structure of the internal buses, the use of caches, and thetypes and arrangements of input/output (I/O) device interfaces.

Every processor comes with a unique set of operational codes or commandsthat represent the computer’s instruction set. An instruction set is the set ofmachine instructions that a processor recognizes and can execute. Today, two in-struction set strategies, complex instruction set computer (CISC) and re-duced instruction set computer (RISC), dominate the processor instructionsets of computer architectures. These two strategies differ by the number of op-erations available and how and when instructions are moved into memory.

A CISC processor contains more than 200 unique coded commands, one forvirtually every type of operation. The CISC design goal is for its instruction setto look like a sophisticated programming language. Inexpensive hardware canthen be used to replace expensive software, thereby reducing the cost of develop-ing software. The penalty for this ease of programming is that CISC processor–based computers have increased architectural complexity and decreased overallsystem performance. In spite of these drawbacks, most computers still use CISCprocessors.

The other, most recent approach is RISC processors, which eliminate many ofthe little-used codes found in the complex instruction set. Underlying RISC de-sign is the claim that a very small subset of instructions accounts for a very largepercentage of all instructions executed. The instruction set, therefore, should bedesigned around a few simple “hardwired” instructions that can be executed veryquickly. The rest of the needed instructions can be created in software.

MicroprocessorArchitecture

The input/output (I/O) devices of a computer are not part of the CPU, but arechannels for communicating between the external environment and the CPU.Data and instructions are entered into the computer through input devices, andprocessing results are provided through output devices. Widely used I/O de-vices are the cathode-ray tube (CRT) or visual display unit (VDU), magnetic stor-age media, printers, keyboards, “mice,” and image-scanning devices.

I/O devices are controlled directly by the CPU or indirectly through specialprocessors dedicated to input and output processing. Generally speaking, I/O de-vices are subclassified into secondary storage devices (primarily disk and tape drives)and peripheral devices (any input/output device that is attached to the computer).


T1.5 INPUT/OUTPUT DEVICES TG1-15

Secondary Storage Secondary storage is separate from primary storage and the CPU, but directlyconnected to it. An example would be the 3.5-inch disk you place in your PC’sA drive. It stores the data in a format that is compatible with data stored in pri-mary storage, but secondary storage provides the computer with vastly increasedspace for storing and processing large quantities of software and data. Primarystorage is volatile, contained in memory chips, and very fast in storing and re-trieving data. In contrast, secondary storage is nonvolatile, uses many differentforms of media that are less expensive than primary storage, and is relativelyslower than primary storage. Secondary storage media include magnetic tape,magnetic disk, magnetic diskette, optical storage, and digital videodisk.

Magnetic tape is kept on a large reel or in a small cartridge or cassette. To-day, cartridges and cassettes are replacing reels because they are easier to use andaccess. The principal advantages of magnetic tape are that it is inexpensive, rel-atively stable, and long lasting, and that it can store very large volumes of data.A magnetic tape is excellent for backup or archival storage of data and can bereused. The main disadvantage of magnetic tape is that it must be searched fromthe beginning to find the desired data. The magnetic tape itself is fragile and mustbe handled with care. Magnetic tape is also labor intensive to mount and dis-mount in a mainframe computer.

Magnetic disks, also called hard disks, alleviate some of the problems as-sociated with magnetic tape by assigning specific address locations for data, sothat users can go directly to the address without having to go through interven-ing locations looking for the right data to retrieve. This process is called direct ac-cess. Most computers today rely on hard disks for retrieving and storing largeamounts of instructions and data in a nonvolatile and rapid manner. The harddrives of 2001 microcomputers provide 10 to 30 gigabytes of data storage.

A hard disk is like a phonograph containing a stack of metal-coated platters(usually permanently mounted) that rotate rapidly. Magnetic read/write heads,attached to arms, hover over the platters. To locate an address for storing or re-trieving data, the head moves inward or outward to the correct position, thenwaits for the correct location to spin underneath.

The speed of access to data on hard-disk drives is a function of the rotationalspeed of the disk and the speed of the read/write heads. The read/write headsmust position themselves, and the disk pack must rotate until the proper infor-mation is located. Advanced disk drives have access speeds of 8 to 12 milliseconds.

A hard disk drive (left) anda magnetic tape cartridge(right).



Magnetic disks provide storage for large amounts of data and instructions thatcan be rapidly accessed. Another advantage of disks over reel is that a robot canchange them. This can drastically reduce the expenses of a data center. Storage Tech-nology is the major vendor of such robots. The disks’ disadvantages are that theyare more expensive than magnetic tape and they are susceptible to “disk crashes.”

In contrast to large, fixed disk drives, one current approach is to combine alarge number of small disk drives each with 10- to 40-gigabyte capacity, developedoriginally for microcomputers. These devices are called redundant arrays of in-expensive disks (RAID). Because data are stored redundantly across many drives, the overall impact on system performance is lessened when one drive mal-functions. Also, multiple drives provide multiple data paths, improving performance.Finally, because of manufacturing efficiencies of small drives, the cost of RAID de-vices is significantly lower than the cost of large disk drives of the same capacity.

Hard disks are not practical for transporting data of instructions from one per-sonal computer to another. To accomplish this task effectively, developers createdthe magnetic diskette. (These diskettes are also called “floppy disks,” a name firstgiven the very flexible 5.25-inch disks used in the 1980s and early 1990s.) Themagnetic diskette used today is a 3.5-inch, removable, somewhat flexible magneticplatter encased in a plastic housing. Unlike the hard disk drive, the read/write headof the diskette drive actually touches the surface of the disk. As a result, the speedof the drive is much slower, with an accompanying reduction in data transfer rate.However, the diskettes themselves are very inexpensive, thin enough to be mailed,and able to store relatively large amounts of data. A standard high-density diskcontains 1.44 megabytes. Zip disks are larger than conventional floppy disks, andabout twice as thick. Disks formatted for zip drives contain 250 megabytes.

Optical storage devices have extremely high storage density. Typically, muchmore information can be stored on a standard 5.25-inch optical disk than on a com-parably sized floppy (about 400 times more). Since a highly focused laser beam isused to read/write information encoded on an optical disk, the information can behighly condensed. In addition, the amount of physical disk space needed to recordan optical bit is much smaller than that usually required by magnetic media.

Another advantage of optical storage is that the medium itself is less suscep-tible to contamination or deterioration. First, the recording surfaces (on both sidesof the disk) are protected by two plastic plates, which keep dust and dirt fromcontaminating the surface. Second, only a laser beam of light, not a flying head,comes in contact with the recording surface; the head of an optical disk drivecomes no closer than 1 mm from the disk surface. Optical drives are also less frag-ile, and the disks themselves may easily be loaded and removed. Three commontypes of optical drive technologies are CD-ROM, WORM, and rewritable optical.

Compact disk read-only memory (CD-ROM) disks have high capacityand low cost. CD-ROM technology is very effective and efficient for mass pro-ducing many copies of large amounts of information that does not need to bechanged, for example, encyclopedias, directories, and online databases.

CD-ROMs are generally too expensive for mastering and producing unique,one-of-a-kind applications. For these situations, write once, read many(WORM) technology is more practical. The storage capacity and access forWORMs is virtually the same as for CD-ROMs. Companies use CD-ROM/WORMfor the following applications: publishing their corporate manuals, disseminatingtraining information, and sending samples of products or their description to cus-tomers. Once you write on a WORM it becomes a regular CD-ROM. You cannotchange anything on the disk.

A CD-ROM inside a drive.



Input Devices

When information needs to be changed or updated, and companies do notwant to incur the expense of mastering and producing a new CD-ROM,rewritable optical disks are needed (also called floptical, or magneto-optic). Thesurface of the disk is coated with a magnetic material that can change magneticpolarity only when heated. To record data, a high-powered laser beam heats mi-croscopic areas in the magnetic medium that allows it to accept magnetic pat-terns. Data can be read by shining a lower-powered laser beam at the magneticlayer and reading the reflected light.

DIGITAL VIDEO DISK (DVD). DVD is a new storage disk that offers higher qual-ity and denser storage capabilities. In 2001, the disk’s maximum storage capac-ity is 17 Gbytes, which is sufficient for storing about five movies. It includes su-perb audio (six-track vs. the two-track stereo). Like CDs, DVD comes asDVD-ROM (read-only) and DVD-RAM. Rewritable DVD-RAM systems are al-ready on the market, offering a capacity of 4.7 GB.

Users can command the computer and communicate with it by using one or moreinput devices. Each input device accepts a specific form of data. For example,keyboards transmit typed characters, and handwriting recognizers “read” hand-written characters. Users want communication with computers to be simple, fast,and error free. Therefore, a variety of input devices fits the needs of different in-dividuals and applications (see Table T-1.3). Some of these devices are shown inFigure T-1.5 (page TG1-18) together with their usage.

TABLE T-1.3 Representative Input Devices

Categories

Keying devices

Pointing devices(devices that point to objectson the computer screen)

Optical character recognition(devices that scan characters)

Handwriting recognizers

Voice recognizers(data are entered by voice)

Other devices

Examples

� Punched card reader� Keyboard� Point-of-sale terminal

� Mouse (including rollerballs and trackballs)� Touch screen� Touchpad (or trackpad)� Light pen� Joy stick

� Bar code scanner� Optical character reader� Wand reader� Cordless reader� Optical mark reader

� Pen

� Microphone

� Magnetic ink character readers� Digital cameras� Automatic teller machines (ATM)� Smart cards� Digitizers (for maps, graphs, etc.)


FIGURE T-1.5 Typical input devices. Each input device reads a different form of data for processing by the CPU.(Source: Computing in the Information Age, Stern and Stern, 1993, p. 172. Copyright© 1993 John Wiley & Sons, Inc. Reprinted bypermission of John Wiley & Sons, Inc.)


Voice input is entered,interpreted, and displayed on a screen or saved to disk.

VoiceRecognition

DigitizerDigitizes graphic imagesand transmits them to the computer.

Device

295-488 6078

0

Light Pen or Stylus

Bar Code Reader or Scanner

Keyboard

Mouse

Wand Reader

This is itsy bitsy type not intended to be

read, disected, spindled or muti-

lated.This is itsy bitsy type not intended

to be read, disected, spindled or mutilat-

ed.This is itsy bitsy type not intended to

be read, disected, spindled or

mutilated.This is itsy bitsy type not

intended to be read, disected, spindled

or mutilated.This is itsy bitsy type not in-

tended to be read, disected, spindled or



or mutilated.This is itsy bitsy type not

intended to be read, disected,

spindled or mutilated.This is itsy bitsy

type not intended to be read, disected,

spindled or mutilated.

This is itsy bitsy type not intended to be

read, disected, spindled or muti-

lated.This is itsy bitsy type not intended

to be read, disected, spindled or mutilat-

ed.This is itsy bitsy type not intended to

be read, disected, spindled or



or mutilated.This is itsy bitsy type not in-

tended to be read, disected, spindled or



or mutilated.This is itsy bitsy type not

intended to be read, disected,

spindled or mutilated.This is itsy bitsy

type not intended to be read, disected,

spindled or mutilated.Optical Scanner

Use

Most common formsof data entry.

The data entered isstored as printed bars of different widths.

The data entered is stored on typed pages or even handwritten forms.

The data is entered at the point where a transaction is made.

Touch Screen

Point-of-saleDevice

FOR

Hard Rock Bank & TrustANYWHERE, U.S.A. 54321

I. M. StudentI. M. Student�123456789� 123456780 003 �0000001500�

Magnetic InkCharacterReader

The data entered isimprinted with magnetic ink. This system is mostlyused on bank checks.

Camera,Tape Recorder

Video, photos, graphics, sound, and text can be entered to create multi-media presentations that educate, inform, and entertain.

TOSHIBA



An ergonomic “split” keyboard.

KEYBOARD. The most common input device is the keyboard. The keyboard isdesigned like a typewriter but with many additional special keys. Most computer-users utilize keyboards regularly. Unfortunately, a number of computer users havedeveloped repetitive stress injury, which they allege comes from excessive use ofpoorly designed keyboards (see Chapter 16). As a result, new keyboards havebeen developed that are ergonomically designed. For example, some keyboardsare now “split” in half, loosely approximating the natural angle of the arms andwrists.

Of the many attempts to improve the keyboard, one of the most interestingis the DataHand (datahand.com) keyboard, which consists of two unattached pads.Rather than a conventional array of keys, this device has touch-sensitive recep-tacles (or finger wells) for the fingers and thumbs. Each finger well allows fivedifferent commands, which are actuated by touching one of the sides or the bot-tom of the finger wells. Complex commands can be programmed so that a singleflick of the finger can be used to enter frequently used sequences of commandsor chunks of data.

MOUSE. The computer mouse is a handheld device used to point a cursor at adesired place on the screen, such as an icon, a cell in a table, an item in a menu,or any other object. Once the arrow is placed on an object, the user clicks a but-ton on the mouse, instructing the computer to take some action. The use of themouse reduces the need to type in information or use the slower arrow keys.

Special types of mouses are rollerballs and trackballs, used in many portablecomputers. A new technology, called glide-and-tap, allows fingertip cursor con-trol in laptop computers.

TOUCH SCREEN. An alternative to the mouse or other screen-related devices isa touch screen. The user activates an object on the screen by touching it with hisor her finger.



TOUCHPAD. A touchpad or trackpad is a small, flat, rectangular pointing devicethat is sensitive to pressure and motion.

LIGHT PEN. A light pen is a special device with a light-sensing mechanism, whichis used to touch the screen. Pointing with a light pen is more accurate than usinga touch screen because you can point at very small objects.

JOYSTICK. Joysticks are used primarily at workstations that can display dynamicgraphics. They are also used in playing video games. The joystick moves and po-sitions the cursor at the desired object on the screen.

AUTOMATED TELLER MACHINES. Automated teller machines (ATMs) are interac-tive input/output devices that enable people to obtain cash, make deposits, trans-fer funds, and update their bank accounts instantly from many locations. ATMscan handle a variety of banking transactions, including the transfer of funds tospecified accounts. One drawback of ATMs is their vulnerability to computercrimes and to attacks made on customers as they use outdoor ATMs.

ELECTRONIC FORMS. In form interaction, the user enters data or commandsinto predesignated spaces (fields) in a form (see Figure T-1.6). The headings ofthe electronic form serve as a prompt for the input. The computer may pro-duce some output after input is made, and the user may be requested to con-

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Document creation

• Program designs intelligent forms• Creates relational database• Prints forms with or without data• Develops help screens

Home-officeand field-office

automation platform

Printer

Cigna-Link

Filler LAN packPC processing

EDLforms

Applicationdatabase

Centralized masterElectronic Data Link (EDL)

• Form-filling software• Distribution print software• E-mail distribution• Interactive database applications• Print forms with or without data

Proofprinter

Host

FIGURE T-1.6 Form interaction. Theupper part shows the process of usingelectronic forms, and a completed form isshown on the left. (a) Intelligent electronicform processing (paperless). (Source: BYTEby BYTE Magazine. Copyright © 1993 by CMPMEDIA. Reproduced with permission of CMPMEDIA in the format Textbook via CopyrightClearance Center.)

(b) A standard “service invoice” form.The form appears online to the user whofills in the appropriate information. Theprogram executes automatic routingcomputations (such as sales tax).

(b)

(a)



A POS terminal.

tinue the form interaction process. Electronic forms can alleviate many of theresource-intensive steps of processing forms. Traditional typesetting and printingsteps become unnecessary. Finally, processing centers do not need to rekey datafrom paper-based forms, since the data remain in electronic format throughoutthe process.

WHITEBOARD. A whiteboard is an area on a display screen that multiple userscan write or draw on. Whiteboards are a principal component of teleconferenc-ing applications because they enable visual as well as audio communication.

Source data automation captures data in computer-readable form at the momentthe data are created. Point-of-sale systems, optical bar-codes and code scanners,other optical character recognition devices, handwriting recognizers, voice rec-ognizers, digitizers, and cameras are examples of source data automation. Sourcedata automation devices eliminate errors arising from humans keyboarding dataand allow for data to be captured directly and immediately, with built-in errorcorrection. The major devices are described below.

POINT-OF-SALE TERMINALS. Many retail organizations utilize point of sale (POS)terminals. The POS terminal has a specialized keyboard. For example, the POSterminals at fast-food restaurants include all the items on the menu, sometimeslabeled with the picture of the item. POS terminals in a retail store are equippedwith a scanner that reads the bar-coded sales tag. POS devices increase the speedof data entry and reduce the chance of errors. POS terminals may include manyfeatures such as scanner, printer, voice synthesis (which pronounces the price byvoice), and accounting software.

BAR CODE SCANNER. Bar code scanners scan the black-and-white bars writtenin the Universal Product Code (UPC). This code specifies the name of the productand its manufacturer (product ID). Then a computer finds in the database theprice equivalent to the product’s ID. Bar codes are especially valuable in high-volume processing where keyboard energy is too slow and/or inaccurate. Appli-cations include supermarket checkout, airline baggage stickers, and transportcompanies’ packages (Federal Express, United Parcel Service, and the U.S. PostalService). The wand reader is a special handheld bar code reader that can readcodes that are also readable by people.

Source DataAutomation



OPTICAL CHARACTER READER (OR OPTICAL SCANNER). With an optical charac-ter reader (OCR), source documents such as reports, typed manuscripts, and bookscan be entered directly into a computer without the need for keying. An OCRconverts text and images on paper into digital form and stores the data on diskor other storage media. OCRs are available in different sizes and for differenttypes of applications.

The publishing industry is the leading user of optical scanning equipment.Publishers scan printed documents and convert them to electronic databases thatcan be referenced as needed. Similarly, they may scan manuscripts instead of re-typing them in preparation for the process that converts them into books andmagazines. Considerable time and money are saved, and the risk of introductionof typographical errors is reduced.

HANDWRITING RECOGNIZERS. Today’s scanners are good at “reading” typed orpublished material, but they are not very good at handwriting recognition. Hand-writing recognition is supported by technologies such as expert systems andneural computing and is available in some pen-based computers.

Scanners that can interpret handwritten input are subject to considerable er-ror. To minimize mistakes, handwritten entries should follow very specific rules.Some scanners will flag handwritten entries that they cannot interpret or willautomatically display for verification all input that has been scanned. Becausehandwritten entries are subject to misinterpretation and typed entries can besmudged, misaligned, and/or erased, optical scanners have an error rate muchhigher than the error rate for keyed data.

Pen-based input devices transform the letters and numbers written by userson the tablet into digital form, where they can be stored or processed and ana-lyzed. At present, pen-based devices cannot recognize free-hand writing verywell, so users must print letters and numbers in block form.

VOICE RECOGNIZERS. The most natural way to communicate with computersis by voice, using a natural language. The process of doing this is called naturallanguage processing. Voice recognition devices convert spoken words into dig-ital form. Voice recognition devices are extremely important because they workfast, free the user’s hands, and result in few entry errors. They also allow peo-ple with visual or other disabilities to communicate with computers. When voicetechnology is used in combination with telephones, people can call their com-puters from almost any location. While voice technologies have certain limita-tions such as size of the vocabulary, they are rapidly being improved. In 2001,voice recognizers have a vocabulary of 160,000 to 250,000 words (e.g., Via Voicefrom IBM and Naturally Speaking from Dragon Systems).

Recognizing words is fairly easy, but understanding the content of sentencesand paragraphs is much more difficult. To understand a natural language inquiry,a computer must have sufficient knowledge to analyze the input in order to inter-pret it. This knowledge includes linguistic knowledge about words, domain knowl-edge, common-sense knowledge, and even knowledge about users and their goals.

MAGNETIC INK CHARACTER READERS. Magnetic ink character readers (MICRs) readinformation printed on checks in magnetic ink. This information identifies thebank and the account number. On a canceled check, the amount is also readableafter it is added in magnetic ink.



A digital camera.

DIGITIZERS. Digitizers are devices that convert drawings made with a pen on a sen-sitized surface to machine-readable input. As drawings are made, the images aretransferred to the computer. This technology is based on changes in electrical chargesthat correspond to the drawings. Designers, engineers, and artists use digitizers.

DIGITAL CAMERAS. Regular video cameras can be used to capture pictures thatare digitized and stored in computers. Special cameras are used to transfer pic-tures and images to storage on a CD-ROM. A digital camera can take photos andload them directly from the camera, digitally, to a main storage or secondary stor-age device.

Digital cameras use a charge-coupled device (CCD) instead of film. Once youtake pictures you can review, delete, edit, and save images. You can capture soundor text annotations and send the results to a printer. You can zoom or shrink im-ages and interface with other devices. Images can be transmitted from the cam-era to a PC, printer, or other cameras, even via telephone lines. Digital cameraswork with or without computers.

In addition to instant prints, you can do many other things with your digi-tal camera (cost $200–$1,000). For example, you can stop scribbling notes andcan instead digitally capture the teacher’s (presenter’s) notes, slides, and othervisual exhibits.

The output generated by a computer can be transmitted to the user via severaldevices and media. The presentation of information is extremely important inencouraging users to embrace computers. The major output devices are shownin Figure T-1.7 and are discussed next.

Output Devices

FIGURE T-1.7Representative output devices and their use.(Source: Computing in the Information Age, Stern andStern 1993, p. 199. Copyright© 1993 John Wiley& Sons, Inc. Reprinted bypermission of John Wiley &Sons, Inc.)

Output Device

Printer

Monitor

Plotter

Audio response

Image processingequipment

Prints reports, fills in forms,prints high-quality graphics.

Displays keyed,computer-stored, orcomputer-producedinformation.

Draws computer-producedcolor graphics and charts.

Responds to users withverbal messages or music, and sound and voice overlays for multimedia presentations.

Stores documents, photos, graphics, videos, animations and sound on film, compact disk or laser disk.

Use



MONITORS. The data entered into a computer can be visible on the computermonitor, which is basically a video screen that displays both input and output.Monitors come in different sizes, ranging from inches to several feet, and in dif-ferent colors. The major benefit is the interactive nature of the device.

Monitors employ the cathode ray tube (CRT) technology, in which an electronic“gun” shoots a beam of electrons to illuminate the pixels on the screen. CRTstypically are 21-inch or smaller. The more pixels on the screen, the higher theresolution. Portable computers use a float screen consisting of a liquid crystal dis-play (LCD). Gas plasma monitors offer larger screen sizes (more than 36 inches)and higher display quality than LCD monitors but are much more expensive.

In 2001, we have seen more and more thin and flat monitors on the mar-ket, but the cost is still high ($650 to $5,000).

IMPACT PRINTERS. Like typewriters, impact printers use some form of striking action topress a carbon or fabric ribbon against paper to create a character. The most common im-pact printers are the dot matrix, daisy wheel, and line. Line printers print one line at atime; therefore, they are faster than one-character type printers.

Impact printers are slow and noisy, cannot do high-resolution graphics, andare often subject to mechanical breakdowns. They have largely been replaced bynonimpact printers.

NONIMPACT PRINTERS. Nonimpact printers overcome the deficiencies of impactprinters. Laser printers are of higher speed, containing high-quality devices thatuse laser beams to write information on photosensitive drums, whole pages at atime; then the paper passes over the drum and picks up the image with toner.Because they produce print-quality text and graphics, laser printers are used indesktop publishing and in reproduction of artwork. Thermal printers create wholecharacters on specially treated paper that responds to patterns of heat producedby the printer. Ink-jet printers shoot tiny dots of ink onto paper. Sometimes calledbubble jet, they are relatively inexpensive and are especially suited for low-volumegraphical applications when different colors of ink are required.

PLOTTERS. Plotters are printing devices using computer-driven pens for creat-ing high-quality black-and-white or color graphic images—charts, graphs, anddrawings. They are used in complex, low-volume situations such as engineeringand architectural drawing, and they come in different types and sizes.

VOICE OUTPUT. Some devices provide output via voice—synthesized voice. Thisterm refers to the technology by which computers “speak.” The synthesis of voiceby computer differs from a simple playback of a prerecorded voice by either ana-log or digital means. As the term “synthesis” implies, the sounds that make upwords and phrases are electronically constructed from basic sound componentsand can be made to form any desired voice pattern. The quality of synthesizedvoice is currently very good, and relatively inexpensive.

Multimedia refers to a group of human-machine communication media, someof which can be combined in one application. In information technology, an in-teractive multimedia approach involves the use of computers to improve human-machine communication by using a combination of media. The construction of

An LCD monitor.

Multimedia


REFERENCES AND BIBLIOGRAPHY TG1-25

Laser printers.

A large plotter and its output (on the right).

TABLE T-1.4 Communications Media

Computer� CRT and terminals� CD-ROM� Computer interactive videodisc� Digital video interactive� Compact disc interactive� Computer simulation� Teletext/videotext� Intelligent tutoring system� Hypertext� Image digitizing� Scanners� Screen projection� Object-oriented programming

Motion image� Videodisc (cassette)� Motion pictures� Broadcast television� Teleconference/videoconference

� Animation� Virtual reality

Projected still visuals� Slide� Overhead

Graphic materials� Pictures� Printed job aids� Visual display

Audio� Tape/cassette/record� Teleconference/audioconference� Sound digitizing� Microphone� Compact disc� Music

Text� Printouts

Source: Based on P. Chao, et al., “Using Expert Systems Approaches to Solve Media Selection Prob-lems: Matrix Format,” Proceedings of the Association of Computer Interface Systems, November 1990,IEEE.


a multimedia application is called authoring. Multimedia also merges the capa-bilities of computers with television sets, VCRs, CD players, and other enter-tainment devices. Communications media are listed in Table T-1.4. The multi-media software is described in Technology Guide 2.

REFERENCES AND BIBLIOGRAPHY

1. Athens, G., “Supercomputer Tops 1 Teraflop,” ComputerWorld,January 2, 1997, p. 124.

2. Barry, B. Brey, “The Intel Microprocessors: 8086/8088,80186/80188, 80286, 80386, 80486, Pentium, Pentium Pro,Pentium II Processors.” Upper Saddle River, NJ: Prentice-Hall,August 1999.

3. Dillon, N., “Reliability Counts in RAID,” ComputerWorld,September 21, 1998.

4. Dowd, K., and C. R. Severance, High Performance Computing,2nd ed. Cambridge; MA/Sebastopol, CA: O’Reilly & Associ-ates, 1998.

5. Evans, J. S., and R. H., Eckhouse, Alpha RISC Architecture forProgrammers. Upper Saddle River, NJ: Prentice-Hall PTR, 1999.

6. Hansen, B., “The Dictionary of Computing & Digital Media:Terms & Acronyms,” Abf Content, May 1999.

7. Halfhill, R., “Cheaper Computing,” Byte, April 1997.

8. Hachman, M., “AMD vs. Intel, Which Round Is It?,” Byte,January 22, 2001.

9. Katz, M. (ed.), “Technology Forecast: 1997” (also 1998, 1999,2000). Menlo Park, CA: Price Waterhouse World TechnologyCenter, 1997 (1998), (1999), (2000).

10. Lohr, S., “The Network Computer as the PC’s Evil Twin,” NewYork Times, November 4, 1996.

11. Markcott, J., “Innovative to Double Chip Power May Cut LifeSpan of Computers,” New York Times, September 17, 1997.

12. Mossberg, W., “MMX Has Much to Offer, But Less than HypeSuggests,” Wall Street Journal, February 13, 1997, p. 124.

13. Mueller, S., Upgrading and Repairing PCs, 11th ed. Indianapo-lis, IN: Que Corp, September 1999.

14. Peleg, A., et al., “Intel MMX for Multimedia PCs,” Communi-cations of the ACM, Vol. 40, No. 1, January 1997.

15. Purcell, L., CD-R/DVD: Disc Recording Demystified. New York:McGraw-Hill, 2000.

16. Ramstad, E., “Texas Instruments Makes Chip Offering HugeBoost in Power,” Wall Street Journal, January 31, 1997, p. B3.

17. Tredennick, N., “Microprocessor-based Computers,” Computer,October 1996.

18. Vaughan-Nichols, S., “To NC or Not to NC?” Networker, Vol. 1,No. 1, March–April 1997.

19. Vijayan, J., “Wait for Long-Delayed Itanium Continues,” Com-puterWorld, January 29, 2001.

20. White, T., “Rx for 400 Billion Characters,” Beyond Computing,special advertising section, April 1996.

21. Wohl, A. D., “Defining DVD,” Beyond Computing, November–December 1997.



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